Alzheimer's - INTRODUCTION

SYMPTOMS

BRAIN ABNORMALITIES

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BRAIN ABNORMALITIES - Alzheimer’s Disease


BRAIN ABNORMALITIES - Alzheimer’s Disease

This computer graphic compares the brain of a patient with Alzheimer’s disease, left, with a normal, healthy brain, right. A degenerative disease, Alzheimer’s disease causes brain tissue to shrink and leads to a gradual, irreversible loss of memory and language ability.

The brains of patients with Alzheimer’s have distinctive formations—abnormally shaped proteins called tangles and plaques—that are recognized as the hallmark of the disease. Not all brain regions show these characteristic formations. The areas most prominently affected are those related to memory. (Brain Abnormalities - Alzheimer’s Disease, Abnormally shaped proteins called tangles and plaques, Memory)

Tangles are long, slender tendrils found inside nerve cells, or neurons. Scientists have learned that when a protein called tau becomes altered, it may cause the characteristic tangles in the brain of an Alzheimer’s patient. In healthy brains, tau provides structural support for neurons, but in Alzheimer’s patients this structural support collapses. (Brain Abnormalities - Alzheimer’s Disease, Abnormally shaped proteins called tangles and plaques, Memory)

Plaques, or clumps of fibers, form outside the neurons in the adjacent brain tissue. Scientists found that a type of protein, called amyloid precursor protein, forms toxic plaques when it is cut in two places. Researchers have isolated the enzyme beta-secretase, which is believed to make one of the cuts in the amyloid precursor protein. Researchers also identified another enzyme, called gamma secretase, that makes the second cut in the amyloid precursor protein. These two enzymes snip the amyloid precursor protein into fragments that then accumulate to form plaques that are toxic to neurons. (Brain Abnormalities - Alzheimer’s Disease, Abnormally shaped proteins called tangles and plaques, Memory)

Scientists have found that tangles and plaques cause neurons in the brains of Alzheimer’s patients to shrink and eventually die, first in the memory and language centers and finally throughout the brain. This widespread neuron degeneration leaves gaps in the brain’s messaging network that may interfere with communication between cells, causing some of the symptoms of Alzheimer’s disease. (Brain Abnormalities - Alzheimer’s Disease, Abnormally shaped proteins called tangles and plaques, Memory)

Alzheimer’s patients have lower levels of neurotransmitters, chemicals that carry complex messages back and forth between the nerve cells. For instance, Alzheimer’s disease seems to decrease the level of the neurotransmitter acetylcholine, which is known to influence memory. A deficiency in other neurotransmitters, including somatostatin and corticotropin-releasing factor, and, particularly in younger patients, serotonin and norepinephrine, also interferes with normal communication between brain cells. (Brain Abnormalities - Alzheimer’s Disease, Abnormally shaped proteins called tangles and plaques, Memory)

BRAIN ABNORMALITIES - Alzheimer’s Disease | Abnormally shaped proteins called tangles and plaques | Memory